Build and publish to npm

[d1manson]

To make it easier to use.

Need to decide whether to make the google thing just a demo or actually part of the module. Also need to decide whether to remove all the unneeded code (e.g. map.js). If we keep it, then we should try and maintain full support for normal mapbox-gl-js so that you can use both this and that in the same page without duplicating the code (which is large).